<?php
// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]
// +----------------------------------------------------------------------
// | Copyright (c) 2009 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------
namespace org;

use think\facade\Config;
/**
 * Encrypt实现类
 */
class Encrypt{
    private $_key;
    function __construct() {
        $this->_key = Config::get('authkey');
    }
    public function _setKey($_key){
        $this->_key = $_key;
    }
    /**
     * 加密解密函数
     * @param string $string 加密解密字符串
     * @param string $operation ENCODE DECODE
     * @param string $key 别外key
     * @param int $expiry 过期时间
     * @return string
     */
    public static function authCode($string, $operation = 'DECODE', $key = '', $expiry = 0) {

        $ckey_length = 4; // 随机密钥长度 取值 0-32;
        // 加入随机密钥，可以令密文无任何规律，即便是原文和密钥完全相同，加密结果也会每次不同，增大破解难度。
        // 取值越大，密文变动规律越大，密文变化 = 16 的 $ckey_length 次方
        // 当此值为 0 时，则不产生随机密钥

        $key = md5($key ? $key : Config::get('app.token_prefix'));
        $keya = md5(substr($key, 0, 16));
        $keyb = md5(substr($key, 16, 16));
        $keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length) : substr(md5(microtime()), -$ckey_length)) : '';

        $cryptkey = $keya . md5($keya . $keyc);
        $key_length = strlen($cryptkey);

        $string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0) . substr(md5($string . $keyb), 0, 16) . $string;
        $string_length = strlen($string);

        $result = '';
        $box = range(0, 255);

        $rndkey = array();
        for ($i = 0; $i <= 255; $i++) {
            $rndkey[$i] = ord($cryptkey[$i % $key_length]);
        }

        for ($j = $i = 0; $i < 256; $i++) {
            $j = ($j + $box[$i] + $rndkey[$i]) % 256;
            $tmp = $box[$i];
            $box[$i] = $box[$j];
            $box[$j] = $tmp;
        }

        for ($a = $j = $i = 0; $i < $string_length; $i++) {
            $a = ($a + 1) % 256;
            $j = ($j + $box[$a]) % 256;
            $tmp = $box[$a];
            $box[$a] = $box[$j];
            $box[$j] = $tmp;
            $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));
        }

        if ($operation == 'DECODE') {
            if ((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26) . $keyb), 0, 16)) {
                return substr($result, 26);
            } else {
                return '';
            }
        } else {
            return $keyc . str_replace('=', '', base64_encode($result));
        }
    }
    /**
     * 加密
     * @param string $str 要处理的字符串
     * @return string
     */
    public function encrypt($str) {
        $size = mcrypt_get_block_size(MCRYPT_DES, MCRYPT_MODE_CBC);
        $str = $this->pkcs5Pad($str, $size);
        
		$cipher = mcrypt_module_open(MCRYPT_DES,'','cbc','');
		mcrypt_generic_init($cipher, $this->_key, $this->_key);
		$str = mcrypt_generic($cipher,$str);
		mcrypt_generic_deinit($cipher);
        
        $str = base64_encode($str);
        return $str;
    }
    /**
     * 解密
     * @param string $str 要处理的字符串
     * @return string
     */
    public function decrypt($str) {
        $strBin = base64_decode($str);
        
        $cipher = mcrypt_module_open(MCRYPT_DES,'','cbc','');
		mcrypt_generic_init($cipher, $this->_key, $this->_key);
		$str = mdecrypt_generic($cipher,$strBin);
		mcrypt_generic_deinit($cipher);
        
        $str = $this->pkcs5Unpad($str);
        return $str;
    }
 
    private function pkcs5Pad($text, $blocksize) {
        $pad = $blocksize - (strlen($text) % $blocksize);
        return $text . str_repeat(chr($pad), $pad);
    }
 
    private function pkcs5Unpad($text) {
        $pad = ord($text [strlen($text) - 1]);
        if ($pad > strlen($text)){
            return false;
        }
        if (strspn($text, chr($pad), strlen($text) - $pad) != $pad){
            return false;
        }
        return substr($text, 0, - 1 * $pad);
    }
}